Conventionally, there have been internal mixers (refer to Patent Documents 1 and 2 and the like). An internal mixer includes a mixing chamber to which a mixing material is supplied and a rotor arranged within the mixing chamber. The rotor includes a plurality of mixing blades for mixing the mixing material. By the rotor being rotated, the mixing blade mixes the mixing material.
[Conventional Technique 1] In Patent Document 1 (see FIG. 2 and FIG. 4 of the same document), a technique intended to achieve both distributivity and dispersibility of a mixing material with a non-linear blade (13) is described. In paragraph [0017] of the same document, it is described that the length of a mixing blade (12, 13) in the rotor axis direction is set to 0.65 L or 0.7 L with respect to an entire length (L) of a rotor in the rotor axis direction.
[Conventional Technique 2] In Patent Document 2, a technique intended to obtain a mixed product of a favorable quality by causing the size of a gap (tip clearance) between an apex section of a mixing blade and the inner surface of a mixing chamber to be a predetermined value is described. In paragraph [0035] of the same document, it is described that the length of a mixing blade (13, 14) in the rotor axis direction is set to 0.7 W or 0.65 W with respect to an entire length (W) of a rotor in the rotor axis direction.
In the internal mixers of Conventional Techniques 1 and 2, there is room for improvement in the performance for distribution of a mixing material. When the performance for distribution of a mixing material is low, there is a risk that the mixing time of the mixing material (time required to bring the mixing material to a desired mixed state) increases. Therefore, there is room for improvement in the productivity with the internal mixers of Conventional Techniques 1 and 2.